Physics·Properties of waves · NSSCO 4.3.2
Reflection by mirrors
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Every mirror obeys one beautifully simple rule. In this lesson we meet the normal line, learn the law of reflection (angle of incidence = angle of reflection, both measured from the normal), draw and label the ray diagram the marking-scheme way, and discover why the image in a plane mirror is virtual, upright, the same size, laterally inverted, and as far behind the mirror as you are in front. We finish with the clever everyday uses of mirrors, including the periscope.
What you'll learn in this lesson
By the end you should be able to (NSSCO Physics 4.3.2):
- Identify the normal, the angle of incidence (i) and the angle of reflection (r) at the point a ray strikes a mirror
- Recall and use the law of reflection: angle of incidence = angle of reflection (i = r), measured from the normal
- Perform simple constructions, measurements and calculations on a reflection ray diagram
- Draw a ray diagram to show how a plane mirror forms the image of a point on an object
- Give the characteristics of the image in a plane mirror — virtual, upright, same size, laterally inverted, and as far behind as the object is in front
- Describe everyday applications of reflection, including the uses of mirrors and how a periscope works
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